Flexible sign facing materials are ordinarily used for internally lit signs of length greater than 6 to 10 feet because such materials are readily available in continuous lengths whereby shadow producing seams are not a problem whereas conventional rigid materials, e.g. acrylics and polycarbonates, are available only in panels of short length because of strength problems and thus are not available for use in longer signs without shadow producing seams.
Because of shipping and handling problems, flexible material signs of greater than 12 feet, e.g. those used in canopy and building fascias such as those used for gasoline service stations, are ordinarily assembled at the job site, e.g. by contractors. Conventionally, the light box for the sign is shipped in sections and bolted together at the job site. The top and bottom and ends of the light box are used as the sign frame. The flexible sign facing material is attached at the bottom and then is progressively levered along its length into grooved structure at the top together with a retaining bar whereby the entire facing is attached in stretched condition. This requires special grooving and a special tool with ratchet like action. This is a tedious procedure and requires up to three to four days for four workers for a very large sign. Moreover, assembly is hindered by bad weather, especially strong winds.